454 Intelligence and Miscellaneous Articles. 



millimetres, when they were detached by the constant shaking of the 

 ground which always occurs in a large town, and falling on the bot- 

 tom of the cylinder, got beyond the reach of the conditions necessary 

 for their formation ; were it not for this circumstance, they would 

 certainly have attained a length of half an inch. or more in the course 

 of three or four months. In the same vessel crystals of carbonate 

 of lead (PbO, CO) were also formed, evidently in consequence of 

 the contamination of the chromate of potash by carbonate. 



In a similar manner crystals of calc-spar, rhombic tables of 2CaO, 

 HO, PO b + 4HO, and other acicular crystals of a fatty lustre, which 

 the author regards as 3CaO, PO 5 , were obtained. As the principle 

 of this method may be applied almost universally, and as amorphous 

 carbonate of lead is soluble in 50,00.0 parts of water, and chromate 

 of lead is still less soluble (sulphate of baryta is soluble in 43,000 

 parts of water), we may conclude that the fact of a compound being 

 difficult of solution is no hindrance to its artificial preparation in a 

 crystalline form. In the course of these experiments it was remarked, 

 that the slowness with which these crystals were formed (they were 

 generally only produced in several months) depended upon the fluids 

 only coming together in that time ; the experiment was therefore 

 varied by introducing a glass vessel filled with a dry salt into another 

 containing a saline solution, so that the former was only slightly 

 covered. A considerable precipitate was produced, which was depo- 

 sited upon the undissolved salt. Several days afterwards small 

 crystals were observed upon the amorphous precipitate, which, as 

 the conditions of their formation continued, must constantly in- 

 crease in size. In this manner the author hopes to obtain large cry- 

 stals of heavy spar, calc-spar, sulphate of lead (PbO, SO 3 ), pyromor- 

 phite [3(3PbO, PO 5 + Pb CI)] , apatite, &c. By the diffusion of solu- 

 tions of silica and alumina in potash the author hopes to produce felspar. 



The crystallization of soluble bodies is equally simple. Thus, if 

 a solution of sulphate of iron be put into a beaker, carefully covered 

 with a thin stratum of water, and the beaker filled up with alcohol, 

 crystallization commences in the course of a few hours and proceeds 

 rapidly. Crystals may probably be prepared in the same manner 

 from acid and alkaline, alcoholic, aetherial and other fluids ; and the, 

 separation of two bodies by alteration of the solvent which is so often 

 employedVin organic chemistry, may thus be combined with a sepa- 

 ration by crystallization. 



The identification of the crystals obtained with the minerals does 

 not repose upon chemical analysis. However, the number of com- 

 pounds which might possibly be produced is very limited, and the 

 crystals correspond most exactly with the minerals in their physical 

 and qualitative chemical properties, as well as in their grouping and 

 geometrical form. — Ann. der Chem. und Pharm. vol. lxxxvii. p. 120. 



ON THE PASSIVE STATE OF NICKEL AND COBALT. 

 BY J. NICKLES. 



The curious property possessed by iron of becoming less oxidizable 

 after being placed in contact with fuming nitric acid, has exercised 

 the sagacity, of many chemists and physicists. This passive state is 



